Arduino is a great open-source platform for quickly prototyping your hardware. You can control a motor, LED and many other devices using Arduino. If you are interested in monitoring physical parameters, you can also attach sensors to it and acquire data.
In some applications, one may need advance signal processing for the data that is generated from sensor. This can be easily achieved by controlling Arduino/sensor setup through Matlab app. Matlab app can fetch data from Arduino and then can be used for advance processing and control.
Here is one such scheme: